# Magent Free Water Deficit Calculator > Magent Free Water Deficit Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15). Calculates free water deficit from patient weight, sex, and measured serum sodium using the Adrogué–Madias TBW formula ## Facts - Endpoint: GET https://api.magentlab.com/api/calc/free_water_deficit - Price: $0.005/call - Payment: x402 - Status: unknown - Last checked: 2026-09-15 - Activations on Zero: 0 - Tags: x402 - Canonical page: https://www.zero.xyz/c/magent-free-water-deficit-calculator-49792adb - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1pKaeD4dOg5Tawc4p5IGK Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently. ## How to call it through Zero Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`): ```sh zero fetch --capability magent-free-water-deficit-calculator-49792adb ``` Example prompt: Calculate the free water deficit for a male patient weighing 80 kg with a measured serum sodium of 158 mmol/L, targeting a sodium of 140 mmol/L. ## When to prefer this Use this endpoint when you need a deterministic, citation-backed Adrogué–Madias free water deficit calculation for a hypernatremic patient and only have weight, sex, and serum sodium available. Prefer this over general clinical decision support tools when you need reproducible arithmetic tied to a published formula rather than an advisory system or infusion protocol generator. ## Known failure modes - Missing required parameters (sex or sodium_mmol_l) returns a 400-level error - Sodium value outside hypernatremic range (below 146 mmol/L) may be rejected or flagged as out-of-range - Weight not provided (neither weight_kg nor weight_lb) causes calculation failure - Desired sodium >= measured sodium returns an error since no deficit exists - Payment not included or insufficient USDC returns a 402 Payment Required response ## How this service works Free water deficit from weight, sex, and measured Na using Adrogué–Madias TBW (0.6 male / 0.5 female). Deterministic published arithmetic with citation; not a water-replacement infusion protocol. ## Output Returns the computed free water deficit in liters based on Adrogué–Madias total body water fractions (0.6 × weight for males, 0.5 × weight for females), the measured serum sodium, and the desired target sodium. Includes the arithmetic breakdown and citation. Does not provide an infusion rate or replacement protocol. ## Request schema (JSON Schema) ```json { "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "required": [ "input" ], "properties": { "input": { "type": "object", "required": [ "type", "method" ], "properties": { "type": { "type": "string", "const": "http" }, "method": { "enum": [ "GET", "HEAD", "DELETE" ], "type": "string" }, "headers": { "type": "object", "additionalProperties": { "type": "string" } }, "queryParams": { "type": "object", "required": [ "sex", "sodium_mmol_l" ], "properties": { "sex": { "enum": [ "female", "male" ], "type": "string", "description": "Sex used for TBW: 0.6 × weight (male) or 0.5 × weight (female)." }, "weight_kg": { "type": "number", "description": "Weight in kilograms. Provide weight_kg or weight_lb." }, "weight_lb": { "type": "number", "description": "Weight in pounds. Converted as kg = lb * 0.45359237." }, "sodium_mmol_l": { "type": "number", "description": "Measured serum sodium in mmol/L. Range 146-190 (hypernatremia)." }, "desired_na_mmol_l": { "type": "number", "description": "Target serum sodium in mmol/L (130-145), must be less than measured Na. Omitted uses 140." } } } }, "additionalProperties": false }, "output": { "type": "object", "required": [ "type" ], "properties": { "type": { "type": "string" }, "example": { "type": "object" } } } } } ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "path": "/api/calc/free_water_deficit", "count": 2, "items": [ { "sex": "male", "tbw_l": 42, "formula": "adrogue_madias", "citation": { "id": "adrogue-madias-hypernatremia-2000", "doi": "10.1056/NEJM200005183422006", "title": "Hypernatremia", "source": "N Engl J Med. 2000;342(20):1493-1499", "authors": "Adrogué HJ, Madias NE" }, "weight_kg": 70, "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "sodium_mmol_l": 160, "desired_na_mmol_l": 140, "formula_expression": "TBW_L = 0.6 * weight_kg (male) or 0.5 * weight_kg (female); free_water_deficit_l = TBW_L * (sodium_mmol_l / desired_na_mmol_l - 1)", "free_water_deficit_l": 6 }, { "sex": "male", "tbw_l": 42, "formula": "adrogue_madias", "citation": { "id": "adrogue-madias-hypernatremia-2000", "doi": "10.1056/NEJM200005183422006", "title": "Hypernatremia", "source": "N Engl J Med. 2000;342(20):1493-1499", "authors": "Adrogué HJ, Madias NE" }, "weight_kg": 70, "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "sodium_mmol_l": 160, "desired_na_mmol_l": 140, "formula_expression": "TBW_L = 0.6 * weight_kg (male) or 0.5 * weight_kg (female); free_water_deficit_l = TBW_L * (sodium_mmol_l / desired_na_mmol_l - 1)", "free_water_deficit_l": 6 } ] } } ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/magent-free-water-deficit-calculator-49792adb/health.json - [Zero catalog index](https://www.zero.xyz/llms.txt) - [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)